JP6222807B2 - Medical image processing apparatus, X-ray diagnostic apparatus, and medical image processing program - Google Patents

Description

  Embodiments described herein relate generally to a medical image processing apparatus, an X-ray diagnostic apparatus, and a medical image processing program.

  As one of the blood vessel imaging methods in an X-ray diagnostic apparatus, digital subtraction angiography (DSA) is known. DSA is a technique that collects subtraction image data of X-ray image data before and after injection of a contrast medium into a subject for diagnosis. That is, X-ray image data is collected as mask image data for generating difference image data before injection of a contrast agent. On the other hand, X-ray contrast (contrast) image data is collected by administering a contrast medium. Then, DSA image data is generated for diagnosis by differential processing between the X-ray contrast image data and the mask image data.

  By generating such DSA image data, it is possible to acquire image data from which a shadow unnecessary for blood vessel observation is removed. That is, it is possible to obtain diagnostic image data in which blood vessels stained with a contrast agent are selectively depicted. For this reason, an image useful for blood vessel diagnosis can be displayed.

U.S. Pat. No. 8,050,474

  Even if a typical DSA image is collected as a blood vessel image collected by an X-ray diagnostic apparatus, when cerebral arteriovenous malformation, dural arteriovenous fistula, etc. are diagnosed In some cases, blood vessel images useful for diagnosis are not collected. Specifically, it is often difficult to identify a blood vessel in which a contrast medium flows into a diseased part and to distinguish a blood vessel.

  Therefore, the present invention provides a medical image processing apparatus, an X-ray diagnostic apparatus, and a medical image processing program capable of acquiring a blood vessel image that can more clearly identify a blood vessel in which a contrast agent flows into a diseased part. Objective.

A medical image processing apparatus according to an embodiment of the present invention includes a time phase identification unit, a pixel value scale generation unit, and a blood vessel image generation unit. The time phase specifying unit specifies the time when the concentration of the contrast agent is a specific condition in each pixel of the blood vessel region in the X-ray contrast image data or the DSA image data collected in time series. The pixel value scale generation unit creates a gray scale or a color scale that assigns a pixel value to a time when the concentration of the contrast agent is a specific condition. The blood vessel image generation unit generates blood vessel image data having pixel values based on the gray scale or the color scale. Further, the pixel value scale generation unit creates a plurality of gray scales or a plurality of color scales whose pixel values are shifted in the time direction, and the blood vessel image generation unit is based on the plurality of gray scales or the plurality of color scales. The blood vessel image data is generated as a moving image in which the pixel value of each pixel changes periodically.
The medical image processing apparatus according to the embodiment of the present invention includes a time phase identification unit, a pixel value scale generation unit, and a blood vessel image generation unit. The time phase specifying unit specifies the time when the concentration of the contrast agent is a specific condition in each pixel of the blood vessel region in the X-ray contrast image data or the DSA image data collected in time series. The pixel value scale generation unit creates a gray scale or a color scale that assigns a pixel value to a time when the concentration of the contrast agent is a specific condition. The blood vessel image generation unit generates blood vessel image data having pixel values based on the gray scale or the color scale. Further, the pixel value scale generation unit creates a plurality of gray scales or a plurality of color scales in which the phase of the pixel value change is changed, and the blood vessel image generation unit generates the plurality of gray scales or the plurality of color scales. Based on this, the blood vessel image data is generated as a moving image in which the pixel value of each pixel changes periodically.
An X-ray diagnostic apparatus according to an embodiment of the present invention includes an image acquisition system, a time phase specifying unit, a pixel value scale generating unit, and a blood vessel image generating unit. The image acquisition system collects X-ray contrast image data or DSA image data from the subject in time series . The time phase specifying unit specifies a time at which the concentration of the contrast agent is a specific condition in each pixel of the blood vessel region in the X-ray contrast image data or the DSA image data. The pixel value scale generation unit creates a gray scale or a color scale that assigns a pixel value to a time when the concentration of the contrast agent is a specific condition. The blood vessel image generation unit generates blood vessel image data having pixel values based on the gray scale or the color scale. Further, the pixel value scale generation unit creates a plurality of gray scales or a plurality of color scales whose pixel values are shifted in the time direction, and the blood vessel image generation unit is based on the plurality of gray scales or the plurality of color scales. The blood vessel image data is generated as a moving image in which the pixel value of each pixel changes periodically.
The medical image processing program according to the embodiment of the present invention causes a computer to function as a time phase specifying unit, a pixel value scale generation unit, and a blood vessel image generation unit . The time phase specifying unit specifies the time when the concentration of the contrast agent is a specific condition in each pixel of the blood vessel region in the X-ray contrast image data or DSA image data acquired in time series. The pixel value scale generation unit creates a gray scale or a color scale that assigns a pixel value to a time when the concentration of the contrast agent is a specific condition. The blood vessel image generation unit generates blood vessel image data having pixel values based on the gray scale or the color scale. Further, the pixel value scale generation unit creates a plurality of gray scales or a plurality of color scales whose pixel values are shifted in the time direction, and the blood vessel image generation unit is based on the plurality of gray scales or the plurality of color scales. The blood vessel image data is generated as a moving image in which the pixel value of each pixel changes periodically.

1 is a configuration diagram of an X-ray diagnostic apparatus and a medical image processing apparatus according to an embodiment of the present invention. The figure which shows the method of identifying the inflow time or arrival time of the contrast agent to the blood vessel based on the density | concentration profile of a contrast agent. The figure which shows the 1st example of the color scale allocated to the time phase corresponding to the maximum value of the density | concentration profile of a contrast agent. FIG. 4 is a diagram illustrating a color arrangement example of a color scale illustrated in FIG. The figure which shows the 2nd example of the color scale allocated to the time phase corresponding to the maximum value of the density | concentration profile of a contrast agent. FIG. 6 is a diagram illustrating a color arrangement example of the color scale illustrated in FIG. The figure which shows the example of the parametric image produced | generated in the parametric image production | generation part shown in FIG. The flowchart which shows the operation | movement of the X-ray diagnostic apparatus shown in FIG. 1, and the process in a medical image processing apparatus.

  A medical image processing apparatus, an X-ray diagnostic apparatus, and a medical image processing program according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram of an X-ray diagnostic apparatus and a medical image processing apparatus according to an embodiment of the present invention.

  The X-ray diagnostic apparatus 1 includes an imaging system 2, a control system 3, a data processing system 4, and a console 5. The imaging system 2 includes an X-ray tube 6, an X-ray detector 7, a C-type arm 8, a base 9 and a bed 10. The data processing system 4 includes an A / D (analog to digital) converter 11, a medical image processing device 12, a D / A (digital to analog) converter 13, and a display device 14. The A / D converter 11 may be integrated with the X-ray detector 7 in some cases.

  The X-ray tube 6 and the X-ray detector 7 are fixed to both ends of the C-arm 8 so as to face each other across the bed 10. The C-type arm 8 is held by a base 9. The base 9 includes a motor 9A and a rotation mechanism 9B. By driving the motor 9A and the rotation mechanism 9B, the X-ray tube 6 and the X-ray detector 7 are rotated at high speed like a propeller to a desired position together with the C-type arm 8. Can be made.

  As the X-ray detector 7, a flat panel detector (FPD) or an image intensifier TV (I.I.-TV: image intensifier TV) can be used. The output side of the X-ray detector 7 is connected to the A / D converter 11 of the data processing system 4.

  The control system 3 is a device that drives and controls the photographing system 2 by outputting a control signal to each component constituting the photographing system 2. The control system 3 is connected to a console 5 as an input device, and instruction information such as imaging conditions to the control system 3 can be input from the console 5.

  The imaging system 2 sequentially emits X-rays at different angles from the rotatable X-ray tube 6 to the subject O set on the bed 10 under the control of the control system 3 from a plurality of directions. X-rays that have passed through the subject O are sequentially collected by the X-ray detector 7 as X-ray projection data. The X-ray projection data collected by the X-ray detector 7 is output to the A / D converter 11 as X-ray image data.

  A contrast medium injection device 15 for injecting a contrast medium into the subject O is provided in the vicinity of the subject O set on the bed 10. Then, X-ray contrast imaging of the subject O can be performed by injecting the contrast agent into the subject O from the contrast agent injection device 15. The contrast medium injection device 15 can also be controlled by the control system 3.

  Next, the configuration and function of the medical image processing apparatus 12 will be described.

  The input side of the medical image processing apparatus 12 is connected to the output side of the A / D converter 11. Further, a display device 14 is connected to the output side of the medical image processing device 12 via a D / A converter 13. The medical image processing apparatus 12 is connected to the console 5. The medical image processing apparatus 12 can input instruction information necessary for data processing by operating the console 5.

  In addition to the medical image processing apparatus 12 built in the X-ray diagnostic apparatus 1 illustrated in FIG. 1, a similar medical image processing apparatus is connected to the X-ray diagnostic apparatus 1 as a separate system via a network. May be.

  The medical image processing apparatus 12 includes an image memory 16, a subtraction unit 17, a filtering unit 18, an affine transformation unit 19, a gradation transformation unit 20, and a parametric image generation unit 21. The parametric image generation unit 21 further includes a time phase identification unit 22, a color coding unit 23, and a color scale adjustment unit 24.

  The medical image processing apparatus 12 having such a function can be constructed by causing a computer to read a medical image processing program. However, a circuit may be used to configure the medical image processing apparatus 12.

  The image memory 16 is a storage device for storing X-ray image data collected by the imaging system 2. Therefore, if non-contrast X-ray imaging is performed, non-contrast X-ray image data is stored in the image memory 16, and if contrast medium is injected into the subject O and X-ray imaging is performed, X-ray contrast image data is obtained. It is stored in the image memory 16.

  The subtraction unit 17 generates time-series DSA image data in which contrast blood vessels are rendered by a difference (subtraction) process between non-contrast X-ray image data read from the image memory 16 and time-series X-ray contrast image data Has the function of

  The filtering unit 18 has a function of executing desired filter processing such as a high-frequency emphasis filter, a low-pass filter, and a smoothing filter on arbitrary data.

  The affine transformation unit 19 has a function of executing affine transformation processing such as enlargement, reduction, rotational movement, and parallel movement of X-ray image data in accordance with instruction information input from the console 5.

  The gradation conversion unit 20 has a function of performing gradation conversion of X-ray image data with reference to a LUT (Look Up Table).

  The parametric image generation unit 21 has a function of acquiring a temporal change in the concentration of the contrast agent based on time-series DSA image data or X-ray contrast image data, and a pixel corresponding to a time when the concentration of the contrast agent is a specific condition It has a function of generating parametric image data having a value as blood vessel image data.

  For this purpose, the time phase specifying unit 22 has a function of specifying a time phase in which the concentration of the contrast agent is a specific condition based on a profile representing a temporal change in the concentration of the contrast agent. The color coding unit 23 has a function of assigning a color corresponding to the time phase specified by the time phase specifying unit 22. The color scale adjustment unit 24 has a function of determining a color scale used for color coding in the color coding unit 23.

  The specific conditions for assigning the color include the concentration of the contrast agent corresponding to the time when the contrast agent flows into or reaches the target blood vessel, and conversely, the concentration of the contrast agent corresponding to the time when the contrast agent flows out of the target blood vessel. Can be determined according to the diagnostic purpose. For example, the time required for the specific condition can be a time when the concentration of the contrast agent is a maximum value, a predetermined ratio of the maximum value, or a threshold value.

  FIG. 2 is a diagram illustrating a method for identifying the inflow time or arrival time of a contrast medium into a blood vessel based on the contrast profile of the contrast medium.

  In FIG. 2, the horizontal axis indicates the time phase direction, and the vertical axis indicates the intensity of the DSA image data representing the concentration of the contrast agent or the image signal of the contrast image data. As shown in FIG. 2, focusing on pixels corresponding to blood vessel regions of time-series DSA image data or contrast image data, acquiring a concentration change profile of a contrast agent as a curve whose signal intensity changes with time. Can do.

  A typical density change profile is a curve in which the value gradually increases as the contrast agent flows in and gradually decreases as the contrast agent flows out. Therefore, if the threshold TH for detecting the rise of the curve is set with respect to the value of the concentration change profile, the flow of the contrast agent into the blood vessel of interest starts as the time phase Tth when the concentration of the contrast agent reaches the threshold TH It becomes possible to identify the time phase.

However, when the noise is large, the contrast agent inflow start phase may be erroneously identified. Therefore, a predetermined ratio in the range of 5% to 10% of the maximum value of the contrast agent concentration profile may be used as the threshold value so that the influence of noise is suppressed. Alternatively, a time phase contrast agent has reached the blood vessel, the Phase T _{max / 2} when the concentration of the contrast medium as shown in FIG. 2 reaches 50% of the phase Tmax and the maximum value MAX when the maximum value MAX You may make it detect from a density | concentration profile. In the following, the case where the arrival time phase of the contrast agent is identified will be mainly described as an example.

  When specifying the time phase based on the contrast profile of the contrast agent as shown in FIG. 2 for all pixels and assigning a color corresponding to the specified time phase, the color corresponding to the arrival time of the contrast agent, etc. Can generate parametric image data in which each blood vessel is depicted.

  However, the temporal change in the concentration of the contrast agent may be obtained for pixels representing a plurality of pixels by the moving averaging process. That is, it is possible to reduce the matrix size of the image data that is a target for which the concentration change of the contrast agent is to be obtained, along with the smoothing process. Further, the contrast agent concentration change may be obtained based on image data from which noise has been removed by low-pass filter processing. This can also be referred to as moving average processing and low-pass filter processing for the contrast profile of the contrast agent in the spatial direction.

  The moving averaging process and the low-pass filter process can be executed not only in the spatial direction but also in the time direction. When the moving averaging process and the low-pass filter process are executed in the time direction, the process is executed on the contrast agent concentration profile in the time direction.

  Therefore, parametric image data can be generated based on the temporal change in the concentration of the contrast agent after the moving average process in at least one of the time direction and the spatial direction. Also, parametric image data can be generated based on the temporal change in the concentration of the contrast agent after the low-pass filter processing in at least one of the time direction and the spatial direction. This makes it possible to generate smooth parametric image data from which noise has been removed.

  In addition, parametric image data can be generated based on a temporal change in contrast agent concentration having a data interval shorter than the sampling interval of the contrast agent concentration corresponding to the imaging interval of the X-ray contrast image data. The temporal change in the concentration of the contrast agent having a data interval shorter than the sampling interval of the contrast agent concentration can be obtained by an arbitrary process such as an interpolation process, a curve fitting process using a specific function, or a centroid calculation process. . This makes it possible to identify the arrival time of the contrast medium at each pixel with higher accuracy. In particular, it is more effective when performing at least one of moving average processing and low-pass filter processing.

  FIG. 3 is a diagram illustrating a first example of a color scale assigned to the time phase corresponding to the maximum value of the contrast agent concentration profile.

  Fig. 3 (A) shows the contrast agent concentration at each two-dimensional position (xi, yj) (i = 1, 2, 3, ..., m; j = 1, 2, 3, ..., n). The arrival phase Tmax (xi, yj) of the contrast agent specified based on the profile and the maximum value MAX of the density profile is shown. The contrast medium arrives relatively early at a position close to the injection position of the contrast medium. Accordingly, the specified time phase is also a relatively early time phase. On the other hand, at the position away from the contrast agent injection position, the arrival time of the contrast agent is relatively delayed. Therefore, the specified time phase is also a relatively slow time phase.

  FIG. 3B shows an example of a color scale assigned to the specified time phase as shown in FIG. As shown in FIG. 3 (B), a color pixel composed of an R value, a B value, and a G value in a period Tall from the initial time to the end time of the temporal change in contrast agent concentration acquired as a density profile. By assigning a change in value, a color scale can be created. That is, a color scale can be created by assigning a continuous change in hue to a period Tall from the initial time to the end time of the temporal change in contrast agent concentration.

  Then, according to the color scale as shown in FIG. 3B, a two-dimensional time phase map representing the arrival time phase of the contrast agent can be color-coded. Then, it is possible to generate parametric image data in which blood vessels are depicted in different colors according to the arrival phase of the contrast agent.

  However, as shown in FIG. 3A, when the difference in the contrast agent arrival phase Tmax (xi, yj) between the pixel positions (xi, yj) is relatively small with respect to the range of the color scale. The color change between the pixel positions (xi, yj) is also slight. For this reason, it may be difficult to distinguish blood vessels due to the difference in color.

  In particular, when performing X-ray imaging for the purpose of diagnosing a dural arteriovenous fistula or a cerebral arteriovenous malformation, it is important to observe the blood flow between the artery and the vein. Therefore, it is often necessary to distinguish a plurality of blood vessels having a small difference in the arrival time of the contrast agent.

  Therefore, even when the difference in the arrival time of the contrast medium is small among the plurality of blood vessels, the color scale adjustment unit 24 can change the color scale so that the blood vessels can be distinguished as color differences. FIG. 3C shows an example in which a color scale is created by assigning a continuous change in hue as a change in pixel value multiple times in a period Tall from the initial time to the end time of the contrast agent concentration change over time. Show. That is, it is possible to create a color scale in which a continuous change in hue is periodically repeated.

  The color scale as shown in FIG. 3C designates the pixel value corresponding to the initial time phase of the density profile by the operation of the console 5, the period Tscale of change of the pixel value, and the initial pixel value within the period Tscale. Can be created. Thereby, it is possible to create a color scale in which the change of the pixel value is repeated with the designated initial pixel value and the designated period Tscale. Then, a color arrangement as shown in FIG. 3B can be performed within the same period Tscale. Specifically, it is possible to create a color scale in which the hue that exhibits the maximum value within one period Tscale changes between red, green, and blue.

  FIG. 4 is a diagram illustrating a color arrangement example of the color scale illustrated in FIG.

  In FIG. 4, three orthogonal axes indicate the R value, the G value, and the B value, respectively. The R value and G value corresponding to each time phase within the period Tscale along the sides of the color triangle having the maximum value of R value, the maximum value of G value, and the maximum value of B value as vertices as shown in FIG. And B value can be determined. That is, when the relative time is zero and Tscale, both the G value and the B value are zero and the R value is the maximum value. When the relative time is Tscale / 3, both the R value and the B value are zero and the G value is the maximum. When the value and the relative time are 2Tscale / 3, the color arrangement can be performed so that both the R value and the G value are zero and the B value is the maximum value.

  With such a color arrangement, it is possible to generate parametric image data in which the color changes from red to blue via green and then returns to red as the time phase becomes slower. In addition, about the color between red, green, and blue, it can assign to a time phase so that R value, G value, and B value may change linearly, for example. Alternatively, the R value, the G value, and the B value can be assigned to the time phase so that the angle of the line segment connecting the center of the color triangle and the point on the side changes linearly.

  When parametric image data is generated according to a color scale created by such a color arrangement, it is possible to distinguish blood vessels as color differences even if the difference in the arrival time of contrast agents is slight. That is, the arrival time of the contrast agent can be grasped in detail.

  The color that attracts human attention is red. Therefore, as illustrated in FIG. 4, setting the color of the initial time phase with the earliest arrival time of the contrast agent to red leads to improved visibility. That is, it is effective to set the color value corresponding to the initial time phase of the color scale to the maximum value of the R value. As another example, it is also useful to adjust the initial time phase so that the time phase of interest is red.

  FIG. 5 is a diagram illustrating a second example of the color scale assigned to the time phase corresponding to the maximum value of the contrast agent concentration profile.

  5A is similar to FIG. 3A in each of the two-dimensional positions (xi, yj) (i = 1, 2, 3,..., M; j = 1, 2, 3, .. The contrast agent arrival time phase Tmax (xi, yj) specified based on the contrast profile of the contrast agent and the maximum value MAX of the density profile in.

  Then, a color scale as shown in FIG. 5 (B) in which a change in color pixel value is assigned to a period Tall from the initial time to the end time of the contrast agent concentration with time is shown in FIG. 5 (C). Can be changed. The color scale shown in FIG. 5C is created by assigning a continuous change in hue as a change in pixel value in a specified period. The period for assigning the change in pixel value can be determined by designating the start time phase T1 and the end time phase T2. The start time phase T1 and the end time phase T2 can be specified by selecting from time-series X-ray contrast images or DSA images.

  FIG. 6 is a diagram illustrating a color arrangement example of the color scale illustrated in FIG.

  In FIG. 6, three orthogonal axes indicate the R value, the G value, and the B value, respectively. As in FIG. 4, the R value, G value, and B value corresponding to each time phase within the period specified along the sides of the color triangle can be determined. That is, as illustrated in FIG. 4, in the start time phase T1, both the G value and the B value are zero and the R value is the maximum value, and in the intermediate time phase between the start time phase T1 and the end time phase T2, Coloring can be performed such that both the value and the B value are zero and the G value is the maximum value, and in the end phase T2, the R value and the G value are both zero and the B value is the maximum value.

  When the color arrangement as shown in FIG. 6 is performed, a color scale in which the hue exhibiting the maximum value between the start time phase T1 and the end time phase T2 changes among red, green, and blue can be created. In other words, it is possible to create a color scale that changes from red to green through blue within a specified period.

  A pixel value different from the change in the pixel value in the designated period can be assigned to a period other than the designated period. For example, the hue can be changed within and outside a specified period. As a more specific example, create a color scale that changes from white to red in the time phase before the start time phase T1, and changes from blue to white in the time phase after the end time phase T2. be able to.

  In addition, a transmittance different from the transmittance in the designated period can be assigned to a period other than the designated period. As a specific example, the color scale is changed so that the transparency changes from the maximum value to zero in the time phase before the start time phase T1, and the transparency changes from zero to the maximum value in the time phase after the end time phase T2. Can be created. That is, the transmittance can be changed within a predetermined range in the time phase outside the designated period. In this case, the color values such as the R value and the B value may not be changed outside the designated period.

  As described above, for the time phase range outside the designated period, at least one of the pixel value including the R value, the G value, and the B value and the transparency can be changed within the designated period.

  The changed color scale as shown in FIGS. 3C and 5C can be dynamically changed. Specifically, a plurality of color scales can be created by changing at least one of the phase and period of the change in the pixel value of the color scale as shown in FIG. 3C or FIG. Changing the phase of the change in the pixel value corresponds to shifting the color scale in the time phase direction. On the other hand, changing the change period of the pixel value corresponds to expanding or contracting the color scale in the time phase direction.

  When color coding of parametric image data is performed using a plurality of color scales having different color arrangements, a plurality of parametric image data corresponding to the plurality of color scales is generated. The generated plurality of parametric image data can be displayed as a moving image in the color scale direction. That is, blood vessel image data can be generated as a moving image according to a plurality of color scales created by changing at least one of the phase and period of change of the pixel value. Thereby, it becomes possible to grasp | ascertain the flow of a contrast agent and a blood flow more easily. In particular, since the human eye has high visibility with respect to red, it is easy to understand the blood flow dynamics in the region of interest by creating a moving image in which red moves from the start time phase T1 to which attention is paid to the end time phase T2.

  As a specific example, if the color is changed in a designated period as shown in FIG. 5C, the color corresponding to each time phase can be temporally changed. In this case, even in the same time phase, the color changes between red, green and blue. In addition, outside the specified period, the colors of the start time phase T1 and the end time phase T2 can be gradually changed to white, or the transmittance can be changed.

  On the other hand, in the case of a color scale in which color values are periodically changed, a plurality of color scales can be created by gradually changing the initial color values in the cycle.

  The color value including the R value, the G value, and the B value can be changed to a value other than the maximum value. That is, when parametric image data is generated using the above-described color scale, the luminance value of a pixel whose contrast agent concentration profile value has not become zero by the low-pass filter process or the like becomes the maximum. That is, depending on the concentration of the contrast medium, the luminance value is maximized for the pixel that the contrast medium has reached.

  Therefore, the luminance value of the parametric image data can be changed so that the concentration of the contrast agent can be grasped. In other words, parametric image data having a luminance value corresponding to the concentration of the contrast agent when the concentration of the contrast agent becomes a specific condition such as a maximum value can be generated as blood vessel image data.

Specifically, assuming that the maximum R value, G value, and B value before the change of the brightness value are R ₀ , G ₀ , and B ₀ , respectively, the brightness value is multiplied by a coefficient k as shown in Equation (1). It is possible to determine the R value, the G value, and the B value after the change.
(R, G, B) = (kR ₀ , kG ₀ , kB ₀ ) (1)

In equation (1), the coefficient k is set to a value between zero and 1 corresponding to the concentration of the contrast agent. The coefficient k can be determined by, for example, Expression (2).
k = P (x, y) / P ₀ (2)
However, in Equation (2), P (x, y) is the maximum value of the contrast agent concentration profile at the position (x, y) acquired as the image signal value of the X-ray contrast image data or DSA image data. P ₀ is a constant.

  When the coefficient k is set according to the equation (2), the coefficient k is a value proportional to the contrast agent concentration profile value P (x, y). Accordingly, the luminance values (R, G, B) of the parametric image data can also be set to luminance values proportional to the contrast agent concentration profile value P (x, y). In addition, it is possible to sufficiently reduce the luminance value of a pixel having a contrast agent concentration at a noise level or a pixel in which noise actually occurs.

The constant P ₀ can be the maximum value in the spatial direction of the concentration profile value P (x, y) of the contrast agent or an arbitrary value determined empirically. However, if the constant P ₀ is set to a value smaller than the maximum value of the contrast agent concentration profile value P (x, y), the coefficient k may be larger than 1 by the calculation of the equation (2). is there. In such a case, the coefficient k may be set to 1.

  Then, when the pixel value whose value is adjusted by the expression (1) is assigned to each pixel position (x, y), parametric image data in which blood vessels are rendered with colors and brightness according to the arrival phase and density of the contrast agent Can be generated. It should be noted that the adjustment of the luminance value shown in Expression (1) can be executed at the time of color coding in the color coding unit 23.

  As described above, the parametric image data generated by the parametric image generation unit 21 can be displayed on the display device 14 in the same manner as the X-ray contrast image data and the DSA image data. Moreover, parametric image data can be preserve | saved at the image memory 16 as needed.

  FIG. 7 is a diagram illustrating an example of a parametric image generated by the parametric image generation unit 21 illustrated in FIG.

  As shown in FIG. 7, the parametric image is an image in which the blood vessel into which the contrast agent is injected is displayed in color, and the luminance value is zero in a region where the contrast agent is not present. In addition, the blood vessel is depicted as a region where the color changes according to the arrival time of the contrast agent. For this reason, it is possible to observe how the blood flows together with the contrast agent depending on the color.

  In the X-ray diagnostic apparatus 1 and the medical image processing apparatus 12 having the functions and configurations as described above, an image that collects at least X-ray contrast image data from the subject O through the cooperation of the imaging system 2 and the control system 3. A function as a collection system is provided. In addition, the time phase specifying unit 22 and the color coding unit 23 of the parametric image generating unit 21 cooperate to acquire a temporal change in the concentration of the contrast agent based on at least the X-ray contrast image data, and according to the color scale, It functions as a blood vessel image generation unit that generates blood vessel image data having a pixel value corresponding to a time when the density is a specific condition. Further, the pixel value for creating the color scale by the color scale adjustment unit 24 of the parametric image generation unit 21 assigning the change in pixel value to a period shorter than the period from the initial time to the end time of the contrast agent concentration change over time. It functions as a scale generator.

  However, if the X-ray diagnostic apparatus 1 and the medical image processing apparatus 12 have the same functions as an image acquisition system, a blood vessel image generation unit, and a pixel value scale generation unit, the X-ray diagnostic apparatus 1 and the medical use may be provided depending on other components. The image processing device 12 can be configured. For example, the medical image processing apparatus 12 can be configured by causing a computer to read a medical image processing program that causes the computer to function as a blood vessel image generation unit and a pixel value scale generation unit. In this case, the medical image processing program can be recorded on an information recording medium and distributed as a program product so that a general-purpose computer can be used as the medical image processing apparatus 12.

  Next, operations and actions of the X-ray diagnostic apparatus 1 and the medical image processing apparatus 12 will be described.

  FIG. 8 is a flowchart showing the operation of the X-ray diagnostic apparatus 1 shown in FIG. 1 and the processing in the medical image processing apparatus 12.

  First, in step S1, non-contrast X-ray image data is collected. Specifically, the imaging system 2 moves to a predetermined position under the control of the control system 3, and X-rays are emitted from the X-ray tube 6 toward the subject O set on the bed 10. X-rays transmitted through the subject O are collected as X-ray projection data by the X-ray detector 7. The X-ray projection data collected by the X-ray detector 7 is output to the medical image processing device 12 through the A / D converter 11 as X-ray image data.

  X-ray image data may be collected for one frame or a plurality of frames. If multiple frames of X-ray image data are collected and the filtering unit 18 adds and averages the plurality of frames of X-ray image data, one frame of non-contrast X-ray image data with reduced noise can be generated. The non-contrast X-ray image data acquired in this way is stored in the image memory 16.

  Next, in step S2, X-ray contrast image data is continuously collected. For this purpose, the contrast medium injection device 15 operates under the control of the control system 3 and the contrast medium is injected into the subject O. Then, when a preset time has elapsed from the start of the injection of contrast medium, imaging of X-ray contrast image data is started. Then, X-ray contrast image data is continuously captured in a predetermined period. As a result, time-series X-ray contrast image data is sequentially stored in the image memory 16. The flow of collecting X-ray contrast image data is the same as the flow of collecting non-contrast X-ray image data.

  Next, in step S <b> 3, DSA image data is generated by the subtraction unit 17. In other words, time-series DSA image data is sequentially generated by executing subtraction processing of time-series X-ray contrast image data using non-contrast X-ray image data as mask image data. The generated time-series DSA image data is sequentially stored in the image memory 16.

  The display device 14 can display a time-series X-ray contrast image or DSA image in real time as a live image. Furthermore, a time-series X-ray contrast image or DSA image can be displayed on the display device 14 after X-ray imaging. When a DSA image is displayed afterwards, DSA image data can be generated by subtraction processing only for a time phase period designated by the operation of the console 5.

  Next, in step S <b> 4, the temporal change of the contrast agent concentration is acquired by the time phase specifying unit 22. Specifically, time-series X-ray contrast image data or DSA image data in the time phase period designated by the operation of the console 5 is taken into the time phase specifying unit 22. Then, the time phase specifying unit 22 generates a density profile indicating temporal changes in the density of the contrast agent as shown in FIG. 3A or 5A for each pixel position.

  As the pre-processing or post-processing for generating the contrast agent concentration profile, the filtering unit 18 can execute one or both of the low-pass filter processing and the moving average processing in one or both of the spatial direction and the temporal direction. Thereby, a smooth contrast agent concentration profile with reduced noise can be generated. At the same time, the time phase specifying unit 22 can also generate a contrast agent concentration profile having a data interval shorter than the sampling interval by interpolation processing, calculation of the center of gravity, or curve fitting.

  Next, in step S5, the time phase specifying unit 22 identifies the arrival time phase of the contrast medium for each pixel position based on the contrast profile of the contrast medium. Specifically, the arrival phase of the contrast agent can be identified for each pixel position by data processing such as peak detection processing or threshold processing for the contrast agent concentration profile.

  In addition, after the time phase is specified by data processing such as peak detection processing and threshold processing, interpolation processing, center of gravity calculation, or continuous density profile acquisition by curve fitting is executed only for the period near the specified time phase. You may make it do. In that case, the arrival time phase of the true contrast agent is detected again by data processing such as peak detection processing and threshold processing on the acquired continuous density profile.

  Next, in step S <b> 6, the color scale adjustment unit 24 creates a color scale for color-coding the two-dimensional map of the contrast agent arrival time phase obtained by the time phase specifying unit 22. The color scale adjustment unit 24 is not limited to a general color scale in which the hue continuously changes from the initial time phase to the final time phase at a constant change rate as shown in FIGS. 3 (B) and 5 (B). As shown in FIGS. 3C and 5C, a color scale in which the change rate of the hue of the normal color scale is increased can be created.

  When creating a color scale in which the hue changes continuously and periodically as shown in FIG. 3C, a cycle Tscale in which the hue changes is specified by operating the console 5, and the hue within one cycle Tscale is specified. A color scale can be created by changing. Alternatively, these necessary conditions may be set in advance as default values. Further, the hue at the start time phase within one cycle Tscale can be arbitrarily designated. Furthermore, when the hue in the initial time phase of the concentration change of the contrast agent is not started from the hue of the start time phase within one cycle Tscale, it is necessary to specify the hue corresponding to the initial time phase.

  On the other hand, as shown in FIG. 5C, when creating a color scale having a continuous change in hue different from that outside the specified time phase period within the specified time phase period, A color scale can be created by designating the start time phase T1 and the end time phase T2 to which a specific change is assigned by operating the console 5. The start time phase T1 and the end time phase T2 can be specified by displaying a time-series X-ray contrast image or DSA image on the display device 14 and selecting the image by operating the console 5.

  Next, in step S 7, color coding of the two-dimensional map of the arrival phase of the contrast agent based on the color scale created by the color scale adjusting unit 24 is executed in the color coding unit 23. That is, according to the color scale, R value, G value, and B value corresponding to the arrival time phase of the contrast agent are assigned to each pixel as a pixel value. Thereby, parametric image data is generated.

  At this time, it is desirable to multiply the R value, G value, and B value by a coefficient corresponding to the concentration of the contrast agent in the arrival phase of the contrast agent. As a result, pixels having a relatively high contrast agent concentration in the contrast agent arrival time phase have relatively high luminance values, and conversely, pixels having a relatively small contrast agent concentration in the contrast agent arrival time phase. Can generate parametric image data having a relatively small luminance value.

  The parametric image generated in this way can be displayed on the display device 14. A parametric image can also be displayed as a moving image by shifting or expanding / contracting the color scale in the time phase direction. For this reason, the user can confirm the several blood vessel into which a contrast agent flows by observing a parametric image. In particular, since a change in the hue of the color scale is assigned to a time period that is short, a plurality of blood vessels that are close to the arrival time of the contrast agent can be easily distinguished by the difference in color.

  In other words, the X-ray diagnostic apparatus 1 and the medical image processing apparatus 12 described above perform color coding of a color blood flow image data by color-coding a specific time phase such as the arrival time phase of a contrast medium with a color scale corresponding to the time phase. And the time phase discrimination ability by color is improved by reducing the continuous change of hue on the color scale in the time phase direction.

  Therefore, according to the X-ray diagnostic apparatus 1 and the medical image processing apparatus 12, even if there is a slight difference in contrast agent inflow phase, arrival time phase, or outflow time phase between adjacent blood vessels, the difference in hue As a result, blood vessels can be easily distinguished.

  In particular, in the diagnosis of cerebral arteriovenous malformation or dural arteriovenous fistula, it is important to observe the flow of blood flow to the diseased part between the artery and the vein. Accordingly, it is necessary to distinguish a plurality of blood vessels into which the contrast agent flows. However, since the DSA image is displayed in gray scale, it is difficult to distinguish contrast blood vessels.

  On the other hand, in the X-ray diagnostic apparatus 1 and the medical image processing apparatus 12, the period of the hue change in the color scale can be set short according to the time difference to be identified. As a result, even if a contrast agent flows into a plurality of blood vessels of interest almost simultaneously, the color changes for each blood vessel, so that the blood vessels can be easily distinguished.

  Although specific embodiments have been described above, the described embodiments are merely examples, and do not limit the scope of the invention. The novel methods and apparatus described herein can be implemented in a variety of other ways. Various omissions, substitutions, and changes can be made in the method and apparatus described herein without departing from the spirit of the invention. The appended claims and their equivalents include such various forms and modifications as are encompassed by the scope and spirit of the invention.

  For example, in the embodiment described above, an example in which blood vessel image data is generated as color parametric image data using a color scale has been described, but blood vessel image data may be generated using a gray scale. That is, blood vessel image data having pixel values corresponding to the time when the concentration of the contrast agent is a specific condition according to the gray scale or the color scale can be generated. Further, a gray scale or a color scale can be created by assigning a change in pixel value to a period shorter than the period from the initial time to the end time of the temporal change in the concentration of the contrast agent.

  When blood flow image data is generated using a gray scale, a luminance value is used instead of a hue change as a pixel value change in a period shorter than the period from the initial time to the end time of the contrast agent concentration temporal change. Of continuous changes. Even in that case, the luminance value can be made a value corresponding to the concentration of the contrast agent by multiplying the luminance value by a coefficient k corresponding to the concentration of the contrast agent.

  Similarly, when blood flow image data is generated using a color scale, a continuous change in luminance value can also be assigned as a change in pixel value, as well as a continuous change in hue as described above. . Even in that case, the luminance value can be made a value corresponding to the concentration of the contrast agent by multiplying the luminance value by a coefficient k corresponding to the concentration of the contrast agent.

  As described above, the change in the pixel value assigned to the period shorter than the period from the initial time to the end time of the concentration change of the contrast agent is represented by the continuous change of the hue and the continuous change of the luminance value of the color. Or it can be a continuous change in the gray luminance value.

DESCRIPTION OF SYMBOLS 1, 1A X-ray diagnostic apparatus 2 Imaging system 3 Control system 4 Data processing system 5 Console 6 X-ray tube 7 X-ray detector 8 C type arm 9 Base 9A Motor 9B Rotation mechanism 10 Bed 11 A / D converter 12 Computer 13 D / A converter 14 Display device 15 Contrast medium injection device 16 Image memory 17 Subtraction unit 18 Filtering unit 19 Affine conversion unit 20 Gradation conversion unit 21 Parametric image generation unit 22 Time phase identification unit 23 Color coding unit 24 Color scale adjustment unit O Subject

Claims (19)

A time phase specifying unit for specifying the time when the concentration of the contrast agent is a specific condition in each pixel of the blood vessel region in the X-ray contrast image data or DSA image data collected in time series,
A pixel value scale generating unit for creating a gray scale or a color scale for assigning a pixel value to a time when the concentration of the contrast agent is a specific condition;
A blood vessel image generation unit for generating blood vessel image data having pixel values based on the gray scale or the color scale;
With
The pixel value scale generation unit creates a plurality of gray scales or a plurality of color scales with pixel values shifted in the time direction,
The medical image processing device, wherein the blood vessel image generation unit generates the blood vessel image data as a moving image in which pixel values of the pixels change periodically based on the plurality of gray scales or the plurality of color scales. A time phase specifying unit for specifying the time when the concentration of the contrast agent is a specific condition in each pixel of the blood vessel region in the X-ray contrast image data or DSA image data collected in time series,
A pixel value scale generating unit for creating a gray scale or a color scale for assigning a pixel value to a time when the concentration of the contrast agent is a specific condition;
A blood vessel image generation unit for generating blood vessel image data having pixel values based on the gray scale or the color scale;
With
The pixel value scale generation unit creates a plurality of gray scales or a plurality of color scales in which the phase of changes in pixel values is changed,
The medical image processing device, wherein the blood vessel image generation unit generates the blood vessel image data as a moving image in which pixel values of the pixels change periodically based on the plurality of gray scales or the plurality of color scales. The pixel value scale generation unit is configured to create the gray scale or the color scale by allocating a change in pixel value a plurality of times during a period from an initial time to an end time of a temporal change in the concentration of the contrast agent. The medical image processing apparatus according to claim 1 or 2 to be performed. The pixel value scale generator is a medical image processing apparatus according to claim 1 or 2, wherein configured to generate the gray scale or the color scale by assigning a pixel value change in a specified time period. The medical image processing according to claim 3, wherein the pixel value scale generation unit is configured to create a gray scale or a color scale in which a change in the pixel value is repeated at a specified initial pixel value and a specified period. apparatus.   The blood vessel image generation unit is configured to generate blood vessel image data having a luminance value corresponding to the concentration of the contrast agent when the concentration of the contrast agent satisfies the specific condition. The medical image processing apparatus according to any one of claims. The blood vessel image generation unit is configured to generate the blood vessel image data by setting a time when the concentration of the contrast agent is a maximum value, a predetermined ratio of the maximum value, or a threshold value for the concentration as a time corresponding to the specific condition. The medical image processing apparatus according to any one of claims 1 to 6. Obtains temporal change in contrast agent concentration based on at least X-ray contrast image data, and generates blood vessel image data having pixel values corresponding to the time when the contrast agent concentration is a specific condition according to a gray scale or color scale A blood vessel image generation unit that
A pixel value scale generation unit that creates the gray scale or the color scale by assigning a change in pixel value to a period shorter than a period from the initial time to the end time of the time change of the concentration of the contrast agent;
With
The blood vessel image generation unit includes the pixel corresponding to a time at which the concentration of the contrast agent is a specific condition based on a temporal change in the concentration of the contrast agent having a data interval shorter than the sampling interval of the contrast agent concentration. the medical image processing apparatus which is configured to generate the blood vessel image data having a value.   The blood vessel image generation unit is configured to acquire a temporal change in the concentration of the contrast agent having a data interval shorter than a sampling interval of the contrast agent concentration by interpolation processing, curve fitting processing, or centroid calculation processing. The medical image processing apparatus according to claim 8. Obtains temporal change in contrast agent concentration based on at least X-ray contrast image data, and generates blood vessel image data having pixel values corresponding to the time when the contrast agent concentration is a specific condition according to a gray scale or color scale A blood vessel image generation unit that
A pixel value scale generation unit that creates the gray scale or the color scale by assigning a change in pixel value to a period shorter than a period from the initial time to the end time of the time change of the concentration of the contrast agent;
With
The blood vessel image generation unit, based on a temporal change in the concentration of the contrast agent after moving average processing in at least one of the time direction and the spatial direction, the pixel corresponding to a time when the concentration of the contrast agent is a specific condition the medical image processing apparatus which is configured to generate the blood vessel image data having a value. Obtains temporal change in contrast agent concentration based on at least X-ray contrast image data, and generates blood vessel image data having pixel values corresponding to the time when the contrast agent concentration is a specific condition according to a gray scale or color scale A blood vessel image generation unit that
A pixel value scale generation unit that creates the gray scale or the color scale by assigning a change in pixel value to a period shorter than a period from the initial time to the end time of the time change of the concentration of the contrast agent;
With
The blood vessel image generation unit is configured to detect the pixel corresponding to a time when the concentration of the contrast agent is a specific condition based on a temporal change in the concentration of the contrast agent after the low-pass filter process in at least one of the time direction and the spatial direction. the medical image processing apparatus which is configured to generate the blood vessel image data having a value. The pixel value scale generating unit according to claim 4, wherein configured to generate the gray scale or the color scale by assigning a change different from the pixel value of the pixel values in a period other than the period in which the specified Medical image processing apparatus. Obtains temporal change in contrast agent concentration based on at least X-ray contrast image data, and generates blood vessel image data having pixel values corresponding to the time when the contrast agent concentration is a specific condition according to a gray scale or color scale A blood vessel image generation unit that
A pixel value scale generation unit that creates the gray scale or the color scale by assigning a change in pixel value to a period shorter than a period from the initial time to the end time of the time change of the concentration of the contrast agent;
With
The pixel value scale generator is a medical image is configured to generate the gray scale or the color scale by assigning a permeability different permeability at a specified period in a period other than the period of time that is the specified operation apparatus. The pixel value scale generator as a change in pixel values, continuous change in hue, the gray scale or the color by assigning continuous change in the continuous change or gray luminance value of the luminance value of the color The medical image processing apparatus according to claim 1, wherein the medical image processing apparatus is configured to create a scale. An image acquisition system for collecting X-ray contrast image data or DSA image data in time series from the subject;
A time phase specifying unit for specifying the time when the concentration of the contrast agent is a specific condition in each pixel of the blood vessel region in the X-ray contrast image data or the DSA image data;
A pixel value scale generating unit for creating a gray scale or a color scale for assigning a pixel value to a time when the concentration of the contrast agent is a specific condition;
A blood vessel image generation unit for generating blood vessel image data having pixel values based on the gray scale or the color scale;
With
The pixel value scale generation unit creates a plurality of gray scales or a plurality of color scales with pixel values shifted in the time direction,
The X-ray diagnostic apparatus , wherein the blood vessel image generation unit generates the blood vessel image data as a moving image in which pixel values of the pixels change periodically based on the plurality of gray scales or the plurality of color scales . Computer
A time phase specifying unit for specifying the time when the concentration of the contrast agent is a specific condition in each pixel of the blood vessel region in the X-ray contrast image data or DSA image data acquired in time series,
A pixel value scale generating unit for creating a gray scale or a color scale for allocating pixel values for a time when the concentration of the contrast agent is a specific condition; and
A blood vessel image generation unit for generating blood vessel image data having pixel values based on the gray scale or the color scale;
A medical image processing program that functions as :
The pixel value scale generation unit creates a plurality of gray scales or a plurality of color scales with pixel values shifted in the time direction,
The medical image processing program, wherein the blood vessel image generation unit generates the blood vessel image data as a moving image in which pixel values of the pixels change periodically based on the plurality of gray scales or the plurality of color scales . The pixel value scale generation unit creates the gray scale or the color scale so as to assign a change in pixel value to a period shorter than a period from the initial time to the end time of the contrast agent concentration temporal change, The medical image processing apparatus according to claim 1 or 2. The pixel value scale generation unit creates the gray scale or the color scale so as to assign a change in pixel value to a period shorter than a period from the initial time to the end time of the contrast agent concentration temporal change, The X-ray diagnostic apparatus according to claim 15. The pixel value scale generation unit creates the gray scale or the color scale so as to assign a change in pixel value to a period shorter than a period from the initial time to the end time of the contrast agent concentration temporal change, The medical image processing program according to claim 16.

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